Nu, nu&#39;-bis (alkoxymethyl) treatment of hides



United States Patent O 3,294,478 N,N'-BIS(ALKOXYMETHYL) TREATMENT OF HIDES Marcus Sittenfield, 7903 Gilbert St., Philadelphia, Pa. 19138 No Drawing. Filed Aug. 2, 1963, Ser. No. 299,456 16 Claims. (Cl. 894.33)

This invention relates to the treatment of proteinaceous fibrous material to increase its strength, appearance and wear characteristics, and it particularly relates to the treatment of animal hides and the like to obtain an improved tanning and stabilizing effect on the hide or skin that results in an improved type of leather.

Heretofore, animal skins and hides have been converted into leathers by the well-established tanning method whereby the skin or hide was impregnated with a tanning agent such as oak bark or some other form of tannin or with such more modern tanning agents as chrome, zirconium or aluminum salts, or such synthetics as phenols or aldehydes, or various acids, which acted to crosslink the molecules ofthe hide to stabilize the chemical structure thereof, to increase its strength and to increase its abrasion and tear-resistance.

In some of these heretofore-known processes, the hide had to first be tie-pickled (acid removal) prior to being tanned in order to prevent the hide from becoming hard and brittle, and had to be putthrough the so-called fat liquoring process after tanning. This fat liquoring process was necessary because ordinary tanning operations tend to deprive hides of their natural oils and they therefore become hard and stiff. In the fat liquoring process, these natural oils are replaced by placing the hides in a drum and tumbling them in oil-in-water emulsions known as fat liquors. These so-called fat liquors are usually made from raw oils such as cod, neatsfoot, and the like, rendered soluble by emulsifying with typical dispersing agents such as sulfonated oils.

In the ordinary tanning processes, great care had to be exercised to prevent degradation of the hides during the tanning and finishing operations. It also required great care and skill to produce leathers which had sufiiciently good light fastness to prevent color changes during use. In addition it was often difiicult to produce leathers which were relatively light in weight, flexible, had sufliciently good feel and which, neverthless, were possessed of a high strength and tear resistance.

By means of the present invention, the aforesaid problems in the formation of leather are overcome and, in addition, other advantages are provided. For example, degradative changes within the skin or hide are minimized and, in fact, generally eliminated so that the finished leathers have high tensile strength and tear resistance, due, in large part, to the high degree of cross-linking whereby not only are the collagen fibers and other protein materials cross-linked but it is also true of other components of the hide such as carbohydrates. This high degree of cross-linking also increases the crease and wrinkle resistance of the leathers.

By means of the present invention there is also obtained a high degree of polymerization both between the molecules of the treating agent and between the treating agent and the proteinaceous material. This is especially true on the surfaces of the hides as well as the surfaces of the internal fibrous structure which increase the smoothness, the flexibility, and scuff resistance of the leather.

An additional inherent property of leathers produced in accordance with the present invention is a very light and fiuffy grain structure, even in the absence of the fat liquoring process. This fiufliness is due to a lack of compactness among the interstices of the molecular structure with a consequent large amount of air spaces. These air spaces provide a high degree of insulation giving a socalled Warm feel. They also permit a more ready escape of water vapor through the open interstices so that the so-called clamminess, inherent in many other leathers because of locked-in water vapor and accumulations of body perspiration, is missing. The flufiiness of the skin txeture and the smoothness of the surfaces, due to the polymerization of the proteinaceous fibers, obviate the need for the fat liquoring process which is so necessary in the ordinary tanning processes.

It is further to be noted that the active materials used in the present process are water-clear so that the production of white leathers is easy, and that no prior depickling is necessary, although it may be used if desired. This latter property permits the present process to be readily adapted to assembly-line operations because of the elimination of this step as well as the fat liquoring step. It has also been found that the leathers produced in accordance with the present invention have a very soft, suede-like finish on the flesh side and a smooth fine-textured feel on the skin side.

In accordance with the present invention, the above advantages are achieved by treating the hides with the compound N,Nbis (alkoxymethyl) uron of the structural formula:

wherein R and R are alkyl, preferably lower alkyls, but also including higher alkyls of the fatty acid type as well as mixtures of different alkyls.

The above compound, which may also be referred to as 3,5.-bis (alkoxymethyl) tetrahydro-1,3,5-oxdiazin-4- one is commercially produced under the name Dextraset UN, has heretofore been used as a wash-wear finishing agent for cotton fabrics to increase their wrinkle-resistance properties and to improve the resistance of the cotton to chlorine damage after hypochlorite bleaching. However, it has now been surprisingly discovered that it is extremely effective as a cross-linking and polymerizing agent for proteinaceous fibers, which makes it a very eflicient tanning and stabilizing agent for animal hides and skins, uses not hereofore contemplated.

The N,N'-bis (alkoxymethyl) uron is applied to the hide in aqueous solution, preferably accompanied by agitation, at room temperature. An additive in the form of an aqueous solution of an alkali metal salt, such as an aqueous solution of sodium chloride and sodium acetate, or an aqueous solution of sodium sulfate, may be included to prevent undue swelling of the hide during exposure to the treatment of the skin or hide. The pH should be maintained between about 3 and 12, preferably between about 5 to 9, to prevent rapid breakdown of the treating materials or to prevent an undue length of time being required for the cross-linking and polymerization reaction to occur. As little as 2.5% by weight of the N,N'- bis (alkoxymethyl) uron, based on the weight of the hide, provides a very satisfactory product.

Illustrative of the present invention are the following examples:

Example 1 A strip of Cabretta sheepskin, Weighing 30 gms. and in the commercially-supplied pickled condition, was mixed with 50 m ls. of a 50% by weight aqueous solution of N,N'-bis (alkoxymethyl) uron (Dextraset UN) and the mixture was agitated for 2 hours. At the end of this period, the pH of the mixture was observed to be 5.4. The skin was then squeezed dry to the touch by passing it between pressure rollers whereby a major portion of the treating solution was recovered. The skin was then immersed in a 3% by weight aqueous sodium carbonate solution for a period of 10 hours, without agitation, in order to insure thorough penetration and homogeneous impregnation of the sheepskin strip. At the end of this period, the pH of the solution in which the strip was immersed was observed to be 9.3 and when the strip was subjected to the shrink temperature test, it was found to have a shrink temperature of 88 C.

The shrink temperature is that temperature at which the hide, when immersed in a heated water bath, begins to shrink, and is a measure of the conversion of the hide int-o a stabilized leather. The higher the temperature at which the hide begins -to shrink, the greater the molecular stability of the leather. A good quality leather generally has a shrink temperature above 70 C.

The shrink temperature test is conducted by first thoroughly rinsing the hide in running water, then immersing the hide in a bath of pure water, and then slowly raising the temperature of the bath while maintaining constant agitation. In the present instance, a 550 watt electric heater was used as the heating means and the agitation was provided by a mechanical stirrer.

The resulting strip of leather was observed to be very soft and flexible despite the absence of a fat l-iquoring treatment. The hide was white in color and when exposed in a Fadeometer for days, there was no change in color or shade. The skin side of the leather had excellent grain structure with a smooth, fine-textured touch, while the flesh side had a suede-like finish. It was also observed that the leather was odorless, had good sheer resistance and breaking strength and was light in weight.

Example 2 A second sample of Oabretta sheepskin, similar to that used in Example 1 and also weighing 30 gms, was processed in exactly the same way except that the 50 mls. of the 50% solution of the active material was further diluted with water in a ratio of 1 part of the solution to 1 part water. The pH at the end of the first 2 hour period was 5.4 and at the end of the hour period was 8.5. The shrink temperature of the finished leather was 88 0., identical with that of Example 1. The physical characteristics were also identical insofar as they could be observed.

Example 3 The same materials and treatments were used as in Examples 1 and 2 except that the 50 mls. of the 50% solution of the active material was diluted with water in a ratio of 1 part solution to 3 parts water. The only diiference observed was a pH of 8.2 in the final mixture and a shrink temperature of 87 C. rather than 88 C. as in Examples 1 and 2. The characteristics of the leather appeared otherwise to be the same.

In order to illustrate that de-pickling is not necessary in the present process, a test was made utilizing a strip of de-pickled hide. This is shown in the following example:

Example 4 A strip of Cabretta sheepskin weighing 30 gms. was de-pickled by washing it in successive changes of an aqueous solution consisting of 10% by weight sodium chloride and 2.0% by weight sodium acetate. The depickled hide was then mixed with 50 mls. of a 50% by weight aqueous solution of N,N-bis (alkoxymethyl) uron (Dextraset UN) and was thereafter subjected to the same treatment as the sample used in Example 1. The

4 whether or not the hide is de-pickled. The other characteristics were also the same.

It is known that when a hide is contacted with water, the osmotic pressure of the water must be substantially similar to that of the hide, otherwise the hide will act like a sponge, soaking up the water and becoming unduly swelled. In order to prevent this, it may be neces' sary to either increase the concentration of the active material in the water or to provide an additive to increase the osmotic presswre of the water. This is illustrated in the following example where a larger piece of hide is utilized relative to the solution of active material.

Example 5 A strip of Cabretta sheepskin, in the pickled state and weighing 100 ms, was mixed with 30 mls. of a 50% by weight aqueous solution of N,N'-bis (alkoxymethyl) uron (Dextraset UN) and 170 mls. of the sodium chloride-sodium acetate solution, which was used in Example 4 for de pickling. This latter solution was added to the mixture not as a de-pickling agent but as a means for increasing the osmotic pressure of the solu tion. There was no evidence of swelling. The mixture was then treated in similar manner to Example 1.

The resulting leather had a shrink temperature of 88 0., identical to that of the sample in Example 1, and had, in all other observable respects, the same physical characteristics as the sample of Example 1.

For the purpose of illustrating the present invention used with other types of hides than sheepskin, the following example is provided:

Example 6 A strip of calf hide weighing 100 gms. was mixed with 50 mls. of a 50% by weight aqueous solution of N,N'-bis (alkoxymethyl) uron (DeXtraset UN) and 100 mls. of sodium sulfate. The sodium sulfate was used to increase the osmotic pressure of the water to prevent swelling of the hide. The mixture was then permitted to stand at 25 C. for a period of 24 hours. The resultant leather was then washed and dried and was observed to have been bleached white. It was also soft and flutfy and had all the other characteristics set forth in Example 1 with reference to the sheepskin sample.

The N,N'-bis (alkoxymethyl) uron may also be used in combination with other known tanning agents in order to obtain the particular characteristics associated with any of these other tanning agents. In such a combination, much less of the uron compound need be used than is used by itself, the particular amount depending on the type and amount of the other agent.

Although not used in the above examples, it is possible to obtain a more rapid penetration and distribution of the active materials throughout the hide by increasing the temperature of the reaction. In no event, however, should this temperature exceed 15 C. below the shrink temperature of the hide. Alternatively, the treatment time may be accelerated by the exposure of the reactants to ultrasonic sound waves during the treating period.

The above examples provide for a treatment wherein the hide is dipped in the treating solution. However, any other feasible and desirable means of application may be used such as spraying, brushing, calendering,

resulting leather had a shrink temperature of 88 C.,

painting, etc.

It has also been found that in addition to its above-disclosed utility as a means to form highly improved and stabilized leather, the N,N-bis (alkoxymethyl) uron may be advantageously used for the treatment of other proteinaceous materials such as for the softening and straightening of wool and hair, both animal and human, and for the provision of a soft-smooth feel on animal and human skin.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

The invention claimed is:

1. A method of treating an animal hide which comprises impregnating said animal hide with N,N-bis (alkoxymethyl) uron.

Z. A method of treating an animal hide which comprises impregnating the animal hide with an aqueous solution of N,N'-bis '(alkoxyme'thyl) uron.

3. A method of treating an animal hide which comprises saturating said animal hide with an aqueous solution of N,N-bis (alkoxymethyl) uron and then immersing the saturated hide in an alkaline aqueous bath until the molecular structure of the hide has become substantially cross-linked, polymerized and stabilized.

4. The method of claim 3 wherein said hide is in a pickled condition prior to said treatment.

5. The method of claim 3 wherein said hide is dipickled prior to said treatment.

6. A method of treating an animal hide which comprises saturating the animal hide with an aqueous solution containing N,N-bis (alkoxymethyl) uron and an alkali metal salt, and then immersing the saturated hide in an alkaline aqueous bath until the molecular structure of the hide has become substantially cross-linked, polymelrized and stabilized.

7. The method of claim 6 wherein said hide is in a pickled condition prior to said treatment.

8. The method of claim 6 wherein said hide is depickled prior to said treatment.

'9. A method of treating an animal hide which comprises immersing the animal hide in an aqueous solution of N,N-bis (alkoxymethyl) uron for a period of about 2 hours at about 25 C., accompanied by constant agitation, then substantially drying the hide, and then immersing the hide in an alkaline aqueous bath for about 10 hours without agitation.

10. The method of claim 9 wherein said aqueous solution contains about by weight N,N-bis (alkoxymethyl) uron.

11. The method of claim 9 wherein an effective amount of an alkali metal salt is added to said aqueous solution to prevent swelling of the hide.

12. The method of claim 9 wherein said hide is in a pickled condition prior to immersion.

13. The method of claim 9 wherein said hide is depickled prior to immersion.

14. A leather product comprising an animal hide treated by impregnation with N,N'-bis (alkoxymethyl) uron.

15. A leather product formed by the saturation of an animal hide with an aqueous solution of N,N-bis (alkoxymethyl) uron.

16. A tanning process comprising impregnating a skin with an aqueous solution at pH in the range of about 3 to 9 containing 3,5-bis(alkoxymethyl)tetraphydro-1,3,5- oXdiazin-4-one until the skin is tanned.

References Cited by the Examiner UNITED STATES PATENTS 2,373,135 4/1945 Maxwell 260-244 2,373,136 4/1945 Hoover et a1. 260-309 2,516,283 7/1950 Winheim 8-94 2,926,062 2/1960 Gagliardi 8l28 OTHER REFERENCES Marsh, Crease Resisting Resins, page 50, pub. 1962 by William Clowes and Sons, London, England.

NORMAN G. TORCHIN, Primary Examiner.

D. LEVY, Assistant Examiner. 

1. A METHOD OF TREATING AN ANIMAL HIDE WHICH COMPRISES IMPREGNATING SAID ANIMAL HIDE WITH N,N''-BIS (ALKOMETHYL) URON. 